1. Field of the Invention
This invention relates to a syringe assembly and, more particularly, to a disposable hypodermic syringe and needle combination which has a two-part sheath including a first part which is extendable to prevent accidents, abuse and reuse of the syringe assembly after the initial use.
2. Description of the Prior Art
Various types of syringe assemblies for receiving and dispensing medication as well as other materials have been known. In general, the medication or other materials are introduced into the hollow barrel portion either by receiving the same through the needle which communicates with the barrel interior, or by means of a frangible container, such as an ampule, which is placed within the hollow barrel. Applying pressure to the plunger causes the medication or other material to be expressed through the hollow needle.
Hypodermic syringe assemblies are often used for administering medication to patients suffering from infectious diseases. Therefore, it has been considered of great importance in the art to avoid accidents, where doctors, nurses, or other persons suffer puncture wounds from use of hypodermic needles. Presently, the safe disposal of used syringes and needles is considered a serious problem in the art, particularly in light of the recent spread of acquired immune deficiency syndrome (AIDS), and the wide-spread abuse of syringes and needles by addicts for administering illicit drugs.
In order to prevent the incidence of puncture wounds which are sometimes accidentally self-inflicted by doctors and nurses, there has been a need to provide a simple method for immediately covering the hypodermic needle after use. Furthermore, there has been a need to insure that the needles are not re-used and therefore it has been found expedient to develop a means for locking a protective extension over the hypodermic needle after use to protect medical personnel and to prevent the re-use of the disposable syringe.
U.S. Pat. No. 4,702,738 addresses this problem by providing a disposable hypodermic syringe with a retractable and lockable sheath. Other patents, such as U.S. Pat. No. 4,356,822, also disclose a syringe assembly having a sheath which can be extended to cover the needle but which cannot be locked in this extended position. In addition, U.S. Pat. Nos. 4,237,882, 4,416,663, 4,573,972, 4,731,059, 4,139,009 and 3,967,621 all disclose syringe assemblies with various means for protecting the needle either before or after use.